Change CredentialsProvider::TokenListener to use StatusOr<Token> (#945)

* Change CredentialsProvider::TokenListener to use StatusOr

Rather than a token plus error code/msg.

* Eliminate the concept of an invalid Token

Instead, we'll just use StatusOr<Token>. Note that unauthenticated
tokens are handled as a special case; they're created via:
  Token::Unauthenticated()
and are otherwise "valid", though attempting to retrieve the raw token
on one of these tokens will cause an assertion failure.

1 files changed, 2 insertions, 6 deletions

diff --git a/Firestore/core/src/firebase/firestore/auth/credentials_provider.h b/Firestore/core/src/firebase/firestore/auth/credentials_provider.h
index b9a8a24..1aa76df 100644
--- a/Firestore/core/src/firebase/firestore/auth/credentials_provider.h
+++ b/Firestore/core/src/firebase/firestore/auth/credentials_provider.h
@@ -23,6 +23,7 @@
 #include "Firestore/core/include/firebase/firestore/firestore_errors.h"
 #include "Firestore/core/src/firebase/firestore/auth/token.h"
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
+#include "Firestore/core/src/firebase/firestore/util/statusor.h"
 #include "absl/strings/string_view.h"
 
 namespace firebase {
@@ -30,12 +31,7 @@ namespace firestore {
 namespace auth {
 
 // `TokenErrorListener` is a listener that gets a token or an error.
-// token: An auth token as a string, or nullptr if error occurred.
-// error_code: The error code if one occurred, or else FirestoreErrorCode::Ok.
-// error_msg: The error if one occurred, or else nullptr.
-typedef std::function<void(
-    Token token, const int64_t error_code, const absl::string_view error_msg)>
-    TokenListener;
+typedef std::function<void(util::StatusOr<Token>)> TokenListener;
 
 // Listener notified with a User change.
 typedef std::function<void(User user)> UserChangeListener;